Analysis of quality control of rat bone mass measurement in vivo

Objective: To evaluate the influence of age,measurement site and scan style on the precision and accuracy of rat bone mass measurement in vivo with dual energy X-ray absorptiometry（DEXA）. Methods: Bone mass measurement had been performed on 60 virgin female Sprague-Dawley rats since they were 3 months old.Total body BMD and lumbar vertebrae（L₂-5）BMD were measured under two scan styles: total body scan and appendicular scan. Repeated measurement was performed and coefficient of variation（CV）was determined.20 rats were sacrificed at the age of 3,12 and 24 months and the ash weight of 2-5 lumbar vertebrae was measured.The correlation and regression analysis was thus done between ash weight and bone mineral content（BMC）. Results: 1.The precision of total body BMD measurement was kept below the level of 1% during 3-24 months of age and was not influenced by age;2.Lumbar vertebrae BMD was also analyzable from the image of total body scan,and the precision improved significantly with age from 12 months（2.22%-3.36%）;3.Under appendicular scan,the precision of lumbar vertebrae BMD measurement improved with age after 12 months and was significantly higher than that under total body scan（1.55%-1.8%,P＜0.05）;4.Lumbar vertebrae（2-5）BMC were well correlated with ash weight at all ages and under both scan styles,but the variant at the age of 3 months was higher than that at the age of 12 and 24 months. Conclusion: Animal age,measurement site and scan style all influence the precision and accuracy of rat bone mass measurement in vivo with dual-energy X-ray absorptiometry.